Devices and methods for forming air-fuel mixtures

ABSTRACT

Devices and methods in which liquid fuel droplets are supplied into a mixing region of a flowing air stream and in which a heating element, preferably electrical, is used to propagate radiant heat into the fuel droplets with a controlled amount of heat being applied approximately equal to that required to substantially completely vaporize the liquid fuel droplets. Specific features relate to the mounting of the heating elements and to the use of an elongated tubular or flat element between a venturi section and a throttle valve, or an annular element below the throttle valve.

United States Patent [72] inventor Wilmer C. Jordan 2414 N. 76th Court,Elmwood Park, 111. 61529 [21] Appl. No. 792,227 [22] Filed Jan. 15,1969[45] Patented Jan. 19,1971

Continuation-impart of application Ser. No. 653,073, July 13, 1967,which is a continuation-in-part of application Ser. No. 71 27, M2129, .9

[54] DEVICES AND METHODS FOR FORMING AIR- FUEL MIXTURES 9 Claims, 11Drawing Figs.

[52] U.S.Cl 123/122, 123/ 179 [51] 1nt.Cl ..F02m 31/12 [50] FieldofSearch 123/1791'1,

122F,l22Al,122A2,122D,122E

[56] References Cited UNITED STATES PATENTS 909,896 1/1909 Hertzberg etal. 123/122(F) 946,239 1/1910 Low et 123/122(F) 1,110,482 9/1914 Collier123/122(F)" Primary Examiner--Wendell E. Burns Attorney-Alberts, Brezina& Lund ABSTRACT: Devices and methods in which liquid fuel droplets aresupplied into a mixing region of a flowing air stream and in which aheating element, preferably electrical, is used to propagate radiantheat into the fuel droplets with a controlled amount of heat beingapplied approximately equal to that required to substantially completelyvaporize the liquid fuel droplets. Specific features relate to themounting of the heating elements and to the use of an elongated tubularor flat element between a venturi section and a throttle valve, or anannular element below the throttle valve.

DEVICES AND METHODS FOR FORMING AIR-FUEL MIXTURES This application is acontinuation of a copending application entitled Devices and methods forForming Air-Fuel Mixture," filed July 13, 1967 Ser. No. 653,073, whichwas continuation-impart of a copending application entitled Devices forvaporizing and Expanding of Gasoline and Fuel Mixtures Thereof, filedMay 20, 1965, Ser. No. 457,427.

This invention relates to devices and methods for use in formingvolatile air-fuel mixtures for combustion and more particularly todevices for supplying a controlled amount of heat to substantiallycompletely vaporize liquid fuel droplets and to thereby obtain maximumcombustion efficiency upon combustion of the air-fuel mixture. Theprinciples of the invention are generally applicable in any apparatus orsystem in which a volatile air-fuel mixture is formed, but areillustrated herein as applied to a carburetor for an internal combustionengine. The use of the devices and methods of this invention greatlyincrease gas mileage and at the same time results in greateracceleration and power. In addition, engines can be started in subzeroconditions in which they would not otherwise start, engine flooding issubstantially eliminated. and stalling is minimized. By increasing theefficiency of combustion, carbon deposits are destroyed and muchsmoother and more responsive engine performance is obtained.

The prior art is replete with disclosures of various forms of heatingdevices for use with carburetors,designed for heating the housing of acarburetor to prevent icing, for heating the fuel supplied to acarburetor, and for heating the fuel-air mixture leaving a carburetor.Although some improvement may be obtainedfrom the use of such devicesinengine starting, the designs havebeen such thatit would not bepossible to obtain improved efficiency and performance under operatingconditions. Specially constructed carburetors have been required and thedesign of some of the devices is such that excessive restriction andturbulence in theflow of the air and the air-fuel mixture would beproduced. The designs of the prior art devices are such that they wouldnot be capable of continuous operation to improve efficiency. andperformance and none of the prior art devicesare such that they wouldnot be capable of continuous operation to improve efficiency andperformance and none of the prior art devices have been commerciallyacceptable to any significant extent.

Said continuation-impart application discloses improvements upon theprior art arrangementswherein an electric heating element is designedforcontinuous energization to obtain improved gas mileage and accelerationas well as to improve cold weather starting and to minimize-flooding andvapor lock problems. In particular, the heating element is extended intoa region downstream from the region of a venturi section of acarburetor, at which liquid fuel droplets are supplied into a flowingair stream, the element being operative to propagate radiant heat intothe liquid fuel droplets to vaporize the same. That application furtherdiscloses the use of an elongated heating element disposed generallyparallel to and alongside to the flow path of the air-fuel mixture whichhas an important advantage in that maximum radiant heat can bepropagated into thefuel droplets with minimum interference in the flowof the mixture. In addition, that application discloses the dispositionof the heating element immediately dowmtream from the mixing region, theelement being disposed between the venturi section and the throttlevalve.

This feature is important because at this point, the fuel droplets canbe efficiently vaporized without unduly increasing expansion of the fuelvapor or the temperature of the air fuel mixture, which would tend todecrease the efficiency of the engine.

In addition, the copending application discloses a heating element inwhich a resistance wire is supported by insulating means within an outermetal casing, effective to minimize hot spots" and to prolong the lifeof the resistance wire.

The features disclosed in the prior application are very important andhave been used to obtain significant improvements with respect to gasmileage, acceleration, cold weather starts and minimization of floodingand stalling problems. However, it was believed that additionalimprovements might be made and this invention was evolved with thegeneral ob ject of improving upon the devices and methods of the priorapplication.

ln continuing experimental work, it has been found that a furtherimprovement in results can [be obtained through the application of acontrolled amount of heat in vaporizing the fuel, especially whencombined with the feature as disclosed in the copending prior-filedapplication.

In particular, it has been discovered that greatly improved results canbe uniformly obtained, under all operating conditions, by using acontrolled amount of heat approximately equal to that required tosubstantially completely vaporize the liquid fuel droplets. If theamount of heat is less than this value, liquid fuel droplets arecontained in the air-fuel mixture which cannot be effectively burned upin combustion, and a reducedefficiency of combustion results. If theamount of heat is increased substantially beyond this value, it is foundthat little if any increase in efficiency and power is obtained,apparently due to an unduly large expansion of the fuel and an elevationof the temperature of the fuel-air mixture.

The devices and methods of this inventionhave other applications but areparticularly advantageous when applied to an internal combustion enginecarburetor in which gasoline or other liquid fuel is supplied into aventuri section located upstream from a throttle valve. It has beenfound that optimum overall results are obtained when the controlledamount of heat is equal to that required to substantially completelyvaporize the fuel when the throttle valve is fully opened. With thisvalue of a controlled amount of heat, the engine develops maximumacceleration and torque, and the engine can be operated at maximumefficiency under high speed and load conditions. With this value, theincrease in torque and efficiency obtained at low throttle valveopenings is reduced below that which might be obtained with a lowervalue of the controlled amount of heat. However, the reduction is smalland is insignificant under normal operating conditions.

The optimum value of the controlled amount of heat is relatively highand it is found that in addition to an improvement in torque andefficiency, it results in a significant improvement with respect to coldweather starting and with respect to elimination of flooding andelimination of stalling under high moisture conditions. Cold weatherstarting is improved because the amount of heat is sufficient not onlyto completely vaporize the liquid fuel droplets but also to expand thevaporized fuel to cause a mixture to reach the cylinders having a highproportion of vaporized fuel therein. Flooding is minimized because ofthe increased vaporization of the fuel.

High ambient moisture conditions normally interfere with propervaporization of the fuel and produce difficulties with respect tostarting of the engine and also with respect to stalling of an engineafter it is started. By this invention the fuel is substantiallycompletely vaporized as it leaves the mixing region to minimize suchproblems. This feature is particularly important with respect to marineengines or other engines subjected to high moisture conditions.

In accordance with very important. features of the invention,

the amount of heat required with a particular engine and with a heatingelement of a certain size, configuration and placement is determinedthrough use of a certain testing method or by use of an empiricalformula.

In one preferred embodiment of the invention, the'heating element is anelongated tubular electric element similar to that disclosed in theaforementioned prior filed application which produces excellent resultswhen a controlled amount of elec- In a further embodiment of theinvention, an annular heating element surrounds the path of flow of thefuel-air mixture. The annular element may be conveniently located in agasket between the carburetor and the intake manifold of the engine anda number of such elements may be employed equal to the number ofcarburetor barrels.

A specific feature of the invention relates to the provision of holes ina carburetor air cleaner to increase the supply of air to thecarburetor. Without the provision of heating elements in accordance withthis invention, the increase in the supply of air has'no substantialeffect. However, when combined with the devices of this invention,increased acceleration torque and power and increased efficiency areobtained under high acceleration and high speed conditions of operation.

Another specific feature of the invention relates to improved andsimplified means for mounting of the tubular or flat heating element ina carburetor of conventional construction.

This invention contemplates other objects, features and advantages whichwill become more fully apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings which illustratepreferred embodiments, and in which:

FIG. 1 is a top plan view of an air cleaner and carburetor assembly inwhich a fuel vaporizing device is installed in accordance with theprinciples of this invention;

FIG. 2 is a top plan view similar to FIG. 1, but with the cover of theair cleaner removed;

FIG. 3 is a elevational sectional view taken substantially along lineIII-III OF FIG. 2;

FIG. 4 is a sectional view taken substantially along line IV-IV of FIG.3;

FIG. 5 is a sectional view, on an enlarged scale, taken substantiallyalong line V-V OF FIG. 4, and illustrating the internal construction ofa heating element;

FIG. 6 is a sectional view similar to a portion of FIG. 3, illustratinga modified flat form of heating element;

FIG. 7 is a sectional view taken substantially along line VII-VII ofFIG. 6;

FIG. 8 is a sectional view similar to a lower portion of FIG. 3,illustrating a modified arrangement using annular heating elements belowthrottle valves and supported in a gasket;

FIG. 9 is a sectional view taken substantially along line IX-IX of FIG.8 and constituting a top plan view of the gasket with the annularheating elements therein;

FIG. 10 is a graph illustrating how performance characteristics arechanged with variations in amount of heat; and

FIG. 1 l is an electrical circuit diagram.

Reference numeral 10 generally designates an air cleaner and carburetorassembly for an internal combustion engine in which a fuel vaporizingdevice is installed, in accordance with the principles of thisinvention.

The assembly 10 includes an air cleaner 11 having a cover 12 formed withwith a radially extending air intake tube 13 and mounted on a circularbase plate 14, FIG. 2 being a view with the cover 12 removed. The baseplate 14 has a central opening 15 which receives the upper end of ahousing 16 of a carburetor 17. A post 18 projecting upwardly from thecarburetor 17 extends through a hole in the cover 12 to receive a wingnut 19 which is tightened to clamp the cover 12 to the base plate 14. Anannular air filter 20 is disposed between the cover 12 and the baseplate 14 to filter the air passing into the space above the carburetor17.

In accordance with a specific feature of the invention, the restrictionin the passage of air into the carburetor 17 is reduced by drillingholes 21 in the base plate 14 in angularly spaced relation outside theair filter 20. As shown, twenty-four of the holes 21 are provided inequiangularly spaced relation each of which may have a diameter on theorder of one-fourth or three-eights inches. With the holes 21,additional air can be supplied to the carburetor under high accelerationand high speed conditions of operation and increased torque and powercan be obtained when the heating devices of this invention are used.Without the heating devices of this invention, however,

little if any advantage would be obtained by providing the holes 21. Itwill be understood that the supply of air can be increased in otherways, but the provision of the holes 21 is advantageous in that they canbe readily formed by drilling the base plate of a conventional aircleaner.

The illustrated carburetor I7 is a conventional four barrel carburetorin which the housing 16 is formed with two main flow passages 23 and 24and two auxiliary fiow passages 25 and 26. A pair of butterfly throttlevalves 27 and 28 are mounted on a operating shaft 30 which is operatedfrom a foot-operated control through a conventional linkage, not shown.An additional pair ofthrottle valves 31 and 32 are provided at the lowerends of the auxiliary passages 25 and 26 and are mounted on a shaftwhich is connected to the shaft 30 through a conventional linkage, notshown, operative to start to open the auxiliary valves 31 and 32 whenthe main valves 27 and 28 are at an intermediate position and to fullyopen the auxiliary valves 31 and 32 when the main valves 27 and 28 arefully opened. The upper ends of the main passages 23 and 24 receive airfrom a common region which is separated by a wall 34 from a commonregion above the auxiliary passages 25 and 26.

A conventional choke valve plate 35 is provided across the upper ends ofthe main passages 23 and 24 and is mounted on a shaft 36 which isoperated by a conventional mechanism, either automatic or manual. A pairof venturi sections 37 and 38 are supported in the main passages 23 and24 between the choke valve plate 35, by means of a pair of arms 39 and40 which extend from the sidewalls of the carburetor housing 16 andwhich are internally passaged for supply of gasoline or other fuel froma float chamber (not shown) into the venturi sections 37 and 38. Asimilar pair of venturi sections are supported in the auxiliary passages25 and 26.

In accordance with this invention, heating devices in the form of a pairof elongated tubular electric heating elements 43 and 44 are supportedin the main passages 23 and 24 and extend downwardly below the venturisections 37 and 38, the lower ends of the elements 43 and 44 beingpreferably disposed slightly above the throttle valves 27 and 28. Aspacing on the order of one-fourth inch is satisfactory. The elements 43and 44 thus propagate radiant heat into the region immediatelydownstream from the mixing region defined by the venturi sections 37 and38. The radiant heat so propagated does not have any substantial effecton the air, which has comparatively low absorption characteristics, butthe liquid fuel droplets are relatively highly absorptive and as aresult, the liquid droplets are rapidly vaporized by absorption of theradiant heat. It is important that the elements 43 and 44 are elongatedand that they extend in parallel relation alongside and closely adjacentthe flow of the air-fuel mixture from the venturi section. The intensityof the radiant heat decreases approximately as the square of thedistance from a source and therefore is it is important that theelements be as close as possible to the flow path. It is also desirablethat any obstruction of the flow path be minimized and that excessivedirect contact of fuel droplets with the heating element be minimized toobviate undue expansion of the vapors and excessive turbulence.

It is also noted that the heating elements 43 and 44 are disposedalongside portions of the flow paths which are relatively restrictedsuch that the air is passing therethrough at a relatively high velocity,so that minimum heat is imparted to the air while at the same time, theliquid droplets are vaporized from absorption of the radiant heat.

The heating elements 43 and 44 are of identical construction. As shownin FIG. 5, the heating element 43 comprises a metal tube 46 in which acore 47 of ceramic material is disposed having longitudinally extendingslots 48 in which a wire 49 of nichrome or other high resistance metalis wound. The opposite ends of the wire 49 extend through a cap 50 ofceramic material and are connected to the ends of insulated wires 51 and52 which extend through spaghetti tubing members 53 and 54 of insulatingmaterial. With the elements 43 and 44 properly positioned, the tubingmembers 53 and 54 and the corresponding tubing members for the element44 are held tightly against the support rod or post I8 and a C-shapedclamp band 56 is then disposed around the tubing members, with the endsof the band 56 being pulled together by use of a screw 57. Althoughnot'shown, a spacer sheet of insulating material may be disposed betweenthe clamp band 56 and the tubing members, and a safety wire may beprovided, connecting the head of the screw 57 to the support rod 18, soas to ground the clampband 56. i

The spaghetti tubing members and the wires mounted therein are quitestiff to hold the heating elements 43 and 44 in fixed positions aftermounting thereof. The wires from the heating elements may be extendedthrough an opening 58 in the base 14 of the air cleaner, for connectionto an energizing circuit, described hereinafter in connection with FIG.I I.

The illustrated support arrangement for the elements 43 and 44 isadvantageous in that the heating elements can be readily and quicklyinstalled in a carburetor. In addition, the elements 43 and 44 aresuspended in a manner such as to minimize heating the housing 16. Inthis connection, it is noted that heat is propagated from the heatingelements toward the inner surfaces of the housing passages, but due toreflection at such internal surfaces, a portion of the heat is returnedtoward the path of the air-fuel mixture, and with the cylindricalinternal surface of the passage 23, the radiant heat energy can beconcentrated to some extent at the central portion of the passage, wherethe fuel droplets are concentrated.

It is also noted that it is desirable that the venturi sections 37 and38 be heated to a limited extent but excessive heating of the housingand of the fuel passages extending to the venturi section should beavoided because vaporization of the fuel before it reaches the venturisection can prevent proper and unifonn flow of the fuel.

Referring to FIG. FIGS. 6 and 7, reference numeral 60 designates amodified form of heating element which is like the heating elements 43and 44 except that it is not cylindrical but it is flat to provide anenlarged planar area for propagation of radiant heat into the fueldroplets while offering minimum interference with flow. The internalconstruction of the heating element is not shown but it is similar tothat of the elements 43 and 48, a wire being wound on a ceramic core,disposed within a metal casing. The ends of the wire are connected toinsulated wires 61 and 62 and the element 66 may be supported in thesame manner as the elements 43 and 44.

Referring to FIGS. 8 and 9, another modified construction is illustratedin which four electric heating elements 63-66 of annular form aresupported in a gasket 67 between the lower end of the carburetor housing16 and wall 68 of the intake manifold of the engine. The electricheating elements 63 and 64 surround the lower ends of the main flowpassages 23 and 24, below the main throttle valves 27 and 28, while theelements 65 and 66 surround the lower ends of the auxiliary flowpassages, below the auxiliary throttle valves and 32. The elements 63-66are of identical construction, the element 63, for example, comprisingan outer metal case or housing 70 with resistance wires 71 beingsupported within the housing 70 by means of a core 72, preferably of aceramic material.

Preferably, the gasket 70 extends above and below the elements 63-66toprovide heat insulating material between the elements and the housing16 and the wall 68 of the intake manifold. The elements 63-66 serve topropagate radiant heat into the restricted path through which thefuel-air mixture flows and to vaporize the liquid droplets. Thearrangement lacks one important advantage of the other arrangements inthat the dimension of the elements in a direction parallel to thedirection of flow is relatively small and the elements are spaced asubstantial distance from the venturi sections. Like the otherarrangements, however, the arrangement can be installed withoutmodification of an existing carburetor.

It is noted that the use of additional heating elements 65 and 66 forthe auxiliary passages is an advantage under high acceleration and highspeed operating conditions, although the electrical power consumption isincreased. In this connection, additional electric heating elements ofthe type shown in FIGS. 3-7 can be installed in the auxiliary flowpassages to obtain improved results. Further, elements of the type shownin FIGS. 3-7 can be used in combination with the arrangement shown inFIGS. 8 and 9 and it is also noted that annular elements of the typeshown in FIGS. 8 and 9 could be disposed above the throttle valves, withthe carburetor being specially constructed for that purpose.

It requires appreciable time for the elements to reach operatingtemperature and all elements continuously are energized, the elementsbeing preferably being connected in parallel although they could beconnected in series.

It is noted that in each of the illustrated constructions of the heatingelements, an outer metal case or housing is provided within which aresistance wire is supported on a core of insulating material. This typeof construction is advantageous in that the surface temperature of themetal housing is maintained ,at a uniform temperature because of thehigh coefficient of heat conductivity of the metal and the production ofhot spots" is obviated. With the resistance wire being thus protectedfrom sudden changes in temperature, its life is prolonged. In addition,the construction provides greater surface area for contact with liquidfuel droplets and for propagation of radiant heat into the liquid fueldroplets.

As previously indicated, an important feature of the invention is in theuse of a controlled amount of heat and FIG. 10 graphically illustratesthis feature. In this graph, the percentage acceleration change obtainedwith the use of the heating devices is plotted against current throughthe devices. The percentage acceleration change may be measured byoperating an automobile at a certain uniform speed on a level highway,then moving the throttle valve to a certain more fully opened position,and then measuring with a stopwatch the time required to reach a certainhigher speed, preferably with a plurality of measurements being made ateach value of heater current. In changing from one heater current valueto another, time is allowed to insure that the devices reach a uniformtemperature.

In FIG. 10, the curve 74 indicates the percentage acceleration changeobtained with a fully open throttle valve setting. The percentageacceleration change increases more and more rapidly as the heatercurrent is increased until a maximum value is approached. After reachingthe maximum value, the acceleration change reduces quite gradually untila relatively high current is applied. Curve 75 illustrates the type ofcurve obtained with with the throttle valve moved to an intermediatesetting. This curve has the same general shape as the curve 74, but thepeak is reached at a lower current value.

It is very difficult to obtain an accurate measurement of accelerationat low throttle valve settings, but tests indicate that a curve similarto dotted line curve 76' will be obtained.

In explanation of the depicted results, it is noted that underequilibrium or steady state conditions of operation, the electricalpower applied to the heating elements is equal to the heat energy perunit time conducted and radiated from the elements. For thermalradiation, the total emissivepower of a body varies with the fourthpower of absolute temperature, while the electrical power isproportional to the square of. the current. Thus the heat applied to theliquid fuel droplets by direct contact and in the form of radiantenergyincreases approximately as the square of the current. The vaporizationof the fuel droplets increases and the performance improves inapproximately the same fashion until a point is reached at which theliquid droplets are substantially completely vaporized. Thereafter, thecurrent can be increased without any substantial effect uponvaporization but the increased heat serves to elevate the temperatureand to expand the fuelair mixture. This produces a condition in which,in effect, less fuel and air are supplied into the intake manifold andinto the engine cylinders. As a result, the performance is graduallydecreased with the increased current. In this connection, it is notedthat because of the fact that increased vaporization of the fuel isobtained. it is possible to supply a greater amount of air to thecarburetor. accomplished in the illustrated arrangement through theprovision of the holes 21 in the air cleaner base 14. However, withoutthe increased vaporization, no substantial improvement in performance isobtained through the supply of additional air.

When the throttle opening is reduced, the velocity of flow is reducedand the supply of the fuel droplets is reduced so that completevaporization can be obtained at a lower value of cur rent.

It is noted that at a current value indicated by line 77, peakperformance is obtained at the fully opened throttle valve setting. Withthis current value, the performance is reduced at the intermediatethrottle valve setting but only slightly and optimum overall performanceis obtained at the current value 77.

To determine the optimum value of electrical power to be applied with aparticular engine and with a heating element or elements of certainsizes, configuration and placement, the test method set forth above maybe used. In the alternative, the following empirical formula may beused:

where P is the electrical power input to the heating element orelements, in watts;

D is the displacement of the engine in cubic inches;

C is a fuel constant equated to the compression ratio of the engine;

H is a heat factor corresponding to the ratio of the portion of the areaof the heating element which is effective to propagate radiant heat intothe air-fuel mixture to the total area of the element; and

K is a constant having a value of less than 1.5, preferably in the rangefrom 0.8 to 1.1 and most preferably approximately 0.95.

With respect to the constant C, less power need be supplied when ahigher grade of fuel is used as is recommended for higher compressionengines. If a lower grade fuel is to be used with a high compressionratio engine, the power can be increased somewhat.

Likewise, if a higher grade fuel is used with a low compression engine,the power can be reduced somewhat.

With respect to the heat factor H, this may be estimated from thephysical configuration and placement of the heating element or may bedetermined by test. By way of example, with a heating element positionedas shown in FIGS. 3 and 4, a factor of 0.5 is estimated. In particular,more than the lower one-half of the length of the element is directlyopposite the fuel-air mixture path, and the heat propagated from theupper half of the element has some effect, but since one side of theelement is facing the housing wall, a portion of the radiant heat wouldbe absorbed by the wall without being reflected back toward the fuel-airmixture path. Thus it is estimated that about one-half of the heat istransmitted to the fuel-air mixture. In the alternative, the factor maybe determined by determining the power P required to produce optimumresults and then calculating H from the above formula with K being setequal to 0.95.

As an example of the operation of the formula, it may be assumed thatheating elements are constructed and positioned as shown in FIGS. 35, intwo main barrels of a four barrel carburetor for a 1966 Cadillac enginehaving a cubic inch displacement of 429 and a compression ratio of 10.5.Assuming a heat factor H of 0.5, the power P is calculated to beapproximately 86 watts. In actual operation, excellent results have beenobtained with the use of two 42 watt units.

As another example, assume a single heating element in a single barrelcarburetor of a 1966 Ford 6 engine having a cubic inch displacement of240 and a compression ratio of 9.2; with the heating element having asize and placement relative to the carburetor approximately as shown inFIG. 4, a

heat factor H of 0.5 is again assumed. The power P is calculated to be55 watts, In actual practice, excellent results have been obtained withthe use ofa 56 watt heating element.

It is noted that the curves depicted in FIG. 10 show the change inacceleration with changes in heater current, but similar improvementsare obtained with respect to efficiency and gas mileage. Also, as abovenoted, cold weather starting is improved because the amount of heat issufficient not only to completely vaporize the liquid fuel droplets butalso to expand the vaporized fuel and to cause a mixture to reach thecylinders having a high proportion of vaporized fuel therein. Floodingis minimized because of the increased vaporization of the fuel. Theincreased vaporization of the fuel is also very important infacilitating starting under high ambient moisture conditions and also inminimizing stalling of the engine.

FIG. 11 shows an electrical circuit for energizing the heating elements.The elements 43 and 44 are connected in parallel between ground and apoint 79 which is connected through a fuse 80 to a point 81 connectedthrough a line 82 to accessories of the automobile and also connected toswitch terminals engageable by a key-operated switch contact 83 both inthe normal running or ignition position thereof and in the accessory--position thereof. The contact 83 and a second contact 84 are connectedto one terminal of a battery 85 the other terminal of which is connectedto ground. In the ignition position, contact 84 engages a terminalconnected through a line 86 to the ignition system of the engine. Withthis arrangement, the heater elements 43 and 44 are energized in eitherposition of the switch and are always continuously energized when theengine is operating.

In starting, particularly in cold weather, the switch is moved to theaccessory position and the elements are energized for approximately 30seconds to allow the elements to reach an operating temperature. Theaccelerator foot pedal is then depressed approximately four times topump fuel into the carburetor which is vaporized by the heat and thenwhen the switch is moved to the starting position, a very rich mixtureis initially supplied to the engine to cause starting thereofimmediately. It will be understood that the circuit of FIG. 11 may beused with the other types of heating elements.

It is further noted that the invention is not limited to use inconnection with automotive type engines but may be used for marine andaircraft engines or stationary engines as well. In connection withmarine engines, the invention provides an important safety feature inthat the vaporization of the fuel permits starting on a minimum of fuel,to lessen the possibility of tire, and an increased amount of fuel beingneeded to overcome the moisture factor when the device of this inventionis not provided in the carburetor.

It will be understood that modifications and variations may be effectedwithout departing from the spirit and scope of the novel concepts ofthis invention.

I claim:

1. In a method of improving the performance of an internal combustionengine operable under certain normal ranges of load, speed and ambienttemperature conditions, said engine including air-fuel mixing means,flow path means for flow of mixed air and fuel from said mixing meansfor combustion in said engine, and throttle valve means in said flowpath means for controlling said flow of mixed air and fuel, said enginehaving characteristics such that an optimum amount of radiant heatapplied to enhance vaporization of fuel within said flow path means iseffective to cause said engine to develop maximum average torque andacceleration while operating within said normal ranges of load, speedand ambient temperature conditions and with said throttle valve meansfully open, average torque and acceleration being reduced in proportionto a reduction of the amount of radiant heat below said optimum amountand being also reduced in proportion to an increase of the amount ofradiant heat above said optimum amount, the steps of providingelectrical heating means, arranging said heating means for installationin said flow path means to radiate heat into the mixed air and fuel andto enhance vaporization of the fuel, and providing connections forcontinuously supplying an optimum amount of electrical power to saidheating means at all times during operation of said engine, said optimumamount of electrical power being predetermined in accordance with saidcharacteristics of said engine and being effective to cause radiation ofsaid optimum amount of radiant heat from said heating means into thefuelair mixture in said flow path means.

2, In a method as defined in claim I, the step of arranging said heatingmeans for installation on the downstreamside of said throttle valvemeans. i

3. In a method as defined in claim 1,wherein said air fuel mixing meanscomprises a carburetor having a main venturi section and a fuel supplycommunicating with said main venturi section, said throttle valve meansbeing located downstream from said venturi section, the step ofarranging said heating means for installation in said carburetor betweensaid venturisection and said throttle valve means.

4. In a method as defined in claim 1, wherein said engine is of a typeusable to propel a vehicle, said optimum amount of electrical powerbeing determinable by a test comprising the steps of first installingsaid electrical heating means in said fuel air flow path of said engine,changing the electrical current through said heating means in steps fromone current value to another and measuring at each electrical currentvalue the torque and acceleration capabilities of said engine by firstoperating said engine to propel a vehicle at a certain uniform speed ona level highway, then moving said throttle valve means to a fully opencondition and measuring the time required to accelerate to a certainhigher speed on a level highway, said certain uniform speed and saidcertain higher speed corresponding to the limits of the normal range ofspeed of operation of 'said engine and said measurements of acceleration capabilities being performed at average ambient temperatureconditions, said acceleration capabilities being measured at a number ofelectrical'current values sufficient to establish a current value atwhich maximum acceleration is obtained, and said optimum amount of ofelectrical power being determined from the resistance of said heatingmeans and the said current value at which maximum acceleration isobtained. a

5. In apparatus for improving the performance of an internal combustionengine operable under certain normal ranges of load, speed and ambienttemperature conditions, said engine including air-fuel mixing means,flow path means for flow of mixed air and fuel from said mixing meansfor combustion in said engine, and throttle valve means for controllingsaid flow of mixed air and fuel, said engine having characteristics suchthat an optimum amount of radiant heat applied to enhance vaporizationof fuel within said flow path means is effective to cause said engine todevelop maximum average torque and acceleration while operating withinsaid normal ranges of load, speed and ambient temperature conditions andwith said throttle valve means fully open, average torque andacceleration being reduced in proportion to a'reduction of the amount ofradiant heat below said optimum amount and being also reduced inproportion to an increase in the amount of radiant heat above saidoptimum amount, electrical heating means, means arranging saidelectrical heating means for installation in said flow path means, andelectrical connection means arranged for continuously supplying anoptimum amount of electrical power to said heating means at all timesduring operation of said engine, said optimum amount of electrical powerbeing predetermined in accordance with said characteristics of saidengine and being effective to cause radiation of said optimum amount ofradiant heat from said heating means into the air fuel mixture in saidflow path means.

6. ln apparatus as defined in claim. 5, said electric heating meansincluding an electric heating element comprising an outer metalliccasing, insulation means within said casing, and a resistance wiresupported by said insulation means within said casing.

7. ln apparatus as defined in claim 6, said casing being generallycylindrical.

8. In apparatus as defined in claim 6, said casing having a relativelyfiat configuration.

9. [n apparatus as defined in claim 6, wherein said flow path means ofsaid engine are formed by metal wall means, said means arranging saidelectrical heating means for installation in said flow path meanscomprising means for suspending said electric heating element in saidflow path means in a manner such as to minimize direct conduction ofheat from said outer metallic casing to said metal wall means.

2. In a method as defined in claim 1, the step of arrangiNg said heatingmeans for installation on the downstream side of said throttle valvemeans.
 3. In a method as defined in claim 1, wherein said air fuelmixing means comprises a carburetor having a main venturi section and afuel supply communicating with said main venturi section, said throttlevalve means being located downstream from said venturi section, the stepof arranging said heating means for installation in said carburetorbetween said venturi section and said throttle valve means.
 4. In amethod as defined in claim 1, wherein said engine is of a type usable topropel a vehicle, said optimum amount of electrical power beingdeterminable by a test comprising the steps of first installing saidelectrical heating means in said fuel air flow path of said engine,changing the electrical current through said heating means in steps fromone current value to another and measuring at each electrical currentvalue the torque and acceleration capabilities of said engine by firstoperating said engine to propel a vehicle at a certain uniform speed ona level highway, then moving said throttle valve means to a fully opencondition and measuring the time required to accelerate to a certainhigher speed on a level highway, said certain uniform speed and saidcertain higher speed corresponding to the limits of the normal range ofspeed of operation of said engine and said measurements of accelerationcapabilities being performed at average ambient temperature conditions,said acceleration capabilities being measured at a number of electricalcurrent values sufficient to establish a current value at which maximumacceleration is obtained, and said optimum amount of of electrical powerbeing determined from the resistance of said heating means and the saidcurrent value at which maximum acceleration is obtained.
 5. In apparatusfor improving the performance of an internal combustion engine operableunder certain normal ranges of load, speed and ambient temperatureconditions, said engine including air-fuel mixing means, flow path meansfor flow of mixed air and fuel from said mixing means for combustion insaid engine, and throttle valve means for controlling said flow of mixedair and fuel, said engine having characteristics such that an optimumamount of radiant heat applied to enhance vaporization of fuel withinsaid flow path means is effective to cause said engine to developmaximum average torque and acceleration while operating within saidnormal ranges of load, speed and ambient temperature conditions and withsaid throttle valve means fully open, average torque and accelerationbeing reduced in proportion to a reduction of the amount of radiant heatbelow said optimum amount and being also reduced in proportion to anincrease in the amount of radiant heat above said optimum amount,electrical heating means, means arranging said electrical heating meansfor installation in said flow path means, and electrical connectionmeans arranged for continuously supplying an optimum amount ofelectrical power to said heating means at all times during operation ofsaid engine, said optimum amount of electrical power being predeterminedin accordance with said characteristics of said engine and beingeffective to cause radiation of said optimum amount of radiant heat fromsaid heating means into the air fuel mixture in said flow path means. 6.In apparatus as defined in claim 5, said electric heating meansincluding an electric heating element comprising an outer metalliccasing, insulation means within said casing, and a resistance wiresupported by said insulation means within said casing.
 7. In apparatusas defined in claim 6, said casing being generally cylindrical.
 8. Inapparatus as defined in claim 6, said casing having a relatively flatconfiguration.
 9. In apparatus as defined in claim 6, wherein said flowpath means of said engine are formed by metal wall means, said meansarranging said electrical heating means for installation in said flowpath means comprising Means for suspending said electric heating elementin said flow path means in a manner such as to minimize directconduction of heat from said outer metallic casing to said metal wallmeans.